Control apparatus



Nov. 9, 1965 B. s. M. GRANBORG 3,216,231

CONTROL APPARATUS Filed Nov. 7, 1960 4 Sheets-Sheet 1 Nov. 9, 1965 B. s. M. GRANBORG CONTROL APPARATUS 4 Sheets-Sheet 2 Filed Nov. 7. 1960 a 5 2 5 M FH 2 7 m M MH M 5/5 nm E --ETJ 2 i, ,f JB M 1 J||. 6 2 rlllllllll.. W m E wl wf M a M2 Mm w w WM @n uw F 2 il Il. 9 n www; v: /1/ L lllll IIL M xn Fm( f/a 4 4 y 5 n n M w Few 2mn/nf@ FUZZ Nov. 9, 1965 B. s. M. GRANBORG CONTROL APPARATUS 4 Sheets-Sheet 5 Filed NOV. 7, 1960 Nov. 9, 1965 B. s. M. GRANBORG 3,216,231

CONTROL APPARATUS Filed Nov. '7, 1960 4 Sheets-Sheet 4 IN VEN TOR. ffm 5. /M 5mn/@P5 United States Patent O 3,216,231 CONTROL APPARATUS Bertil S. M. Granborg, Madison, Wis., assigner to Wisconsin Alumni Research Foundation, Madison, Wis., a corporation of Wisconsin Filed Nov. 7, 1960, Ser. No. 67,604 23 Claims. (Cl. 72-8) This invention relates to control apparatus and more particularly to positioning control apparatus for incrementally controlling the position of an adjusting member controlling the physical dimension or arrangement of an article of manufacture. In one specific embodiment of the :invention it is adapted to a steel rolling mill.

The automatic control of modern multistand steel rolling mills is an extremely complex problem. The main purpose of rolling is to shape slabs of steel into thin strips by consecutively passing the steel slabs through a number of rolls. Presently, a considerable amount of production losses exist due to strips whose thickness is olf-gauge or of varying thickness. One of the primary reasons for olf-gauge strips is due to the nature of the rolling process, wherein tolerance on the order of 0.001 inch must be regulated under thousands of tons of roll pressure and at a strip speed in excess of 100 feet per second. It has been found that the primary diiiiculty in controlling thickness of the steel strips has been in the time delays of the mechanisms for adjusting roll spacing, which in turn determine the final steel strip thickness.

Generally, rolling mills have one or more mill screwdown units for adjusting roll spacing. The mill screwdown unit comprises a reversible electric motor and a screw shaft. The screw sha-ft has its upper end threaded for engaging with a threaded hole in the header of the mill frame, and the upper end extends through the header of the mill frame. A screw gear unit couples the reversible electric motor to the upper end of the screw shaft. The lower end of the screw shaft rests on the upper surface of a roll bearing. The steel slab to be rolled passes through the rolls and the lower end of the screw shaft exerts pressure on the roll bearing. The pressure on the roll bearing causes the rolls to exert pressure on the steel slab causing it to -be pressed out to the desired strip thickness.

In one example using this mill screw-down arrangement for adjusting roll space, a strip which is off-gauge .01 inch will take about five seconds before it will be corrected, due to time delays in the mill screw-down unit. Thus, at a strip speed of 100 feet per second, 500 feet of strip will `be lost because it is off-gauge.

It has been found that most deviations in the thickness ofthe strips, from the desired thickness, are small. Therefore, a fast acting means of regulating roll spacing is needed which provides only small incremental adjustments.

Broadly, the present invention contemplates the provision of an arrangement for incrementally controlling a positioning or adjusting member for forming, shaping, proling or otherwise controlling the physical dimensions or arrangement of `an article of manufacture or correcting for positioning errors inherent in the operation of a machine, process or system that affect the physical dimensions of the article. This incremental control is effected by continuously measuring or sensing the controlled physical dimension of the finished article to determine if the ldimension has been correctly controlled and, if not, to provide a control signal that immediately corrects for any error in the positioning of the adjusting or control member to minimize the spoilage thereof and thereby the manufacturing costs. In one embodiment of the invention the incremental adjustment or positioning f' n' 3,216,231 ce Patented Nov. 9, 1965 is effected by the use of a magnetostric'tive element in combination with the conventional positioning members used in a machine, process or system. The magnetostrictive element is further arranged to be responsive to a positioning control signal for this purpose.

A specific embodiment of the invention provides a rolling mill with a frame for supporting two parallel rolls. One o-f the rolls is adjustable. Magnetostrictive adjuster units are coupled to the adjustable roll through its roll bearings. The magnetostrictive adjuster units comprise a magnetostrictive member or element with a coil disposed thereabout and is arranged for providing fine incremental roll space adjustments.

A thickness detector is provided for detecting the strip thickness as it comes out from between the rolls. The thickness detector develops an error signal indicative vof the difference between the strip thickness and a predetermined desired thickness. The error signal is amplified for providing .a current signal for energizing the coil of the magnetostrictive adjuster units.

The output circuit of the thickness .detector is also connected to an input circuit of a mill screw-down control unit. The mill screw-down control unit is connected to the motor of a mill screw-down unit and provides an output signal to the motor causing it to provide coarse adjustments of the roll spacing whenever the output current of the amplifier circuit exceeds a predetermined value.

In one embodiment of the invention, the magnetostrictive element of the magnetostrictive ladjuster is a part of the screw shaft of the mill screw-down unit. `In another embodiment ofthe invention, the magnetostrictive element is a portion of the side of the mill frame. Other embodiments of the invention employ mechanical ampliers for amplifying the amount of magnetostrictive adjustments. Thus, it is seen that the magnetostrictive adjuster utilizes magnetostriction to provide a fine adjustment in the roll spacing, whereas the mill screwdown unit provides a coarse mechanical adjustment in the roll spacing.

A better understanding of the present invention may be obtained with reference to the following detailed descri-ption of the figures, of which:

FIG. 1 is a cross-sectional view of a rolling mill with electronic control circuits therefore shown in block diagram and embodying the present invention;

FIG. 2 is a front elevational view of the rolling mill of FIG. l with magnetostrictive adjusters Vadded at the sides of the mill frame;

FIG. 3 is a front elevational view of the right section of the rolling mill of FIG. 2 with a mechanical amplifier added and embodying the invention;

FIG. 4 is a cross-sectional view of the rolling mill of FIG. 1 with an alternate type of mechanical amplier added and embodying the present invention;

FIG. 5 is a graph showing the relative displacement of the rolls of FIG. l, plotted as a function of roll spacing and operating current;

FIG. 6 is a block diagram of the microwave thickness detector unit of FIG. 1;

FIG. 7 is an alternate magnetostrictive adjuster unit for use in FIGS. 1, 2 and 3;

FIG. 8 is a perspective view of a cylindrical member for use in the magnetostrictive adjuster units;

FIG. 9 is a perspective view of a tubular member for use in the magnetostrictive adjusters; and

FIG. 10 is a perspective view of a scroll member for use in the magnetostrictive adjusters.

Refer now to FIGS. 1 and 2, wherein portions of a mill frame 10 are shown which may be a part of a stand of a rolling mill. Two cylindrical rolls 12 and 14 are shown positioned parallel to each other with the roll 12 positioned vertically above the roll 14. The roll 14 has roll bearings 16 and 18 and the roll 12 has roll bearings 20 and 22. The roll bearings 16 and 18, and therefore the roll 14, are rigidly affixed to the mill frame 1t) to form a reference plane. The roll bearings 2() and 22, and therefore the roll 12, are slidably aixed to the mill frame such that when forces are exerted by a steel slab advanced between the rolls 12 and 14 it will cause the roll 12 to move away from the roll 14. A steel slab 23 is shown being pressed into a thin steel strip of controlled thickness by the rolls 12 and 14.

A screw shaft 26 is positioned above the roll bearing 22 for applying pressure on the roll bearing 22 so that the steel slab 23 is pressed between the rolls 12 and 14. The screw shaft 26 has its lower end 28 physically engaging the top of the roll bearing 22 and its upper end threaded (not shown) for engaging the threads (not shown) on the header of the mill frame 10 in a conventional fashion.

The lower portion 28 of the screw shaft 26 has a coil 30 disposed thereabout. The coil 30 is arranged to apply a magnetic eld lengthwise through the lower portion 28 of the screw shaft 26 whenever the coil 30 is energized by a current signal.

The upper portion of the screw shaft 26 may be a conventional screw shaft material such as steel, whereas the lower portion 28 of the screw shaft 26 must be a ferromagnetic material made of a cobalt-iron'alloy or other material which exhibits a positive magnetostriction or increases in length when subjected to a magnetic field produced by current in the coil 30. The lower end 28 of the screw shaft 26 must be of sufficient length and the coil 30 must'have a sufficient number of turns that from zero current to the maximum desired current in the coil 30 the lower end 28 of the screw shaft 26 will undergo the total desired incremental displacement or change in length and, therefore, change in the roll spacing. When determining the total effective change in length, one must take into account the total deflection or spring constant of the mill frame 10, the bearings 18 and 22 and the compressibility of the screw shaft 26. The material of the lower end 28 of the screw shaft 26 and the turns of the coil 36 must also be selected such that the ferromagnetic material will not be operated in magnetostrictive saturation at any point over the total expected range of current excitation.

It should also be noted that the invention may be practiced in an existing rolling mill without extensive alterations thereof. This may be done by inserting the magnetostrictive adjuster 24 between the lower end of a screw shaft and the roll bearings.

A mill screw-down unit 32 is provided for making coarse adjustments in spacing between the rolls 12 and 14. The mill screw-down unit 32 is of the usual construction and, as shown, comprises a screw gear unit 34 which is mechanically aflixed to the mill frame 1t). The upper end of the screw shaft 26 rotatably engages gears (not shown) which are in the screw gear unit 34. The screw gear unit 34 has an input shaft connected to an output shaft of a motor unit 36. The screw gear unit 34 provides the proper gear ratio between the output shaft of the motor unit 36 and the upper end of the screw shaft 26 for providing the desired coarse adjustments of roll spacing or rough positioning of the roll 12. The motor 36 is a conventional, heavy duty, directcurrent, compound motor. The motor has its input circuits connected to the output circuit of a mill screwdown control unit 38.

Referring now to FIGURE 2, a mill screw-down unit 41 and a magnetostrictive adjuster 39 are also provided for the roll bearing and are identical to the mill screwdown unit 32 and the magnetostrictive adjuster 24 of FIGURE 1. The magnetostrictive adjuster also has a screw shaft and a coil, but the lower end of the screw shaft engages the roll bearing 20 rather than xthe roll bearing 22 and, therefore, exerts forces on the opposite end of the roll 12. The coils of the magnetostrictive adjusters 24 and 39 are connected in parallel and are connected to the output circuit of a thickness detector unit 40. Similarly, the input circuits of the motor units of the mill screw-down units 32 and 41 are connected in parallel and are connected to the output circuits of the mill screw-down control unit 38.

Although the arrangements described in FIGS. l and 2 have the magnetostrictive adjusters connected in a parallel circuit arrangement, they could be connected in series circuit relation and then connected to the thickness detector unit 40 without departing from the invention. It should be noted, however, that the range of output current of the thickness detector unit 40 would then need to be proportionately reduced.

Referring again to FIGURE 1, thickness detector unit 40 detects the thickness of a strip after it passes through the rolls 12 and 14 and develops a signal proportional to the difference between the desired thickness of the strip and the actual thickness of the strip. In the rolling mill of FIG. 1 the thickness detector is a microwave type of thickness gauge which comprises two antennas 42 and 44 and a microwave thickness detector 46. The microwave antennas 42 and 44 radiate a microwave signal toward opposite sides of the strip whose thickness is to be measured. The antennas 42 and 44 also receive the microwave signals which are reflected back from the strip. The microwave signals received lby the antennas 42 and 44 are than transmitted to input circuits of the microwave thickness detector 46. An adjustable desired thickness reference signal generator 4S has an output circuit 47 for developing an electrical output signal corresponding to the desired thickness of the strip. The output circuit 47 of the desired thickness reference signal generator 48 is connected to an input circuit of the microwave thickness detector 46. The microwave thickness detector 46 is responsivel to the reference signal from the signal generator 48 and the microwave signals from the antennas 42 and 44 for providing an error signal corresponding to the difference between the desired thickness, as indicated by the output signal of the signal generator 48, and the actual thickness of the strip, as indicated by the microwave signals.

Referring now to FIG. 6, a block diagram is shown of the microwave thickness detector 46. T he antenna 44 is connected to a separator circuit 100. The separator circuit has a slotted line or wave guide circuit 102 coupled to a directional coupler circuit 104. The slotted line 0r wave guide circuit 102 is connected to the antenna' 44 and the directional coupler is connected to a detector circuit 106. The separator circuit 100 develops an output signal which is related to the microwave signal reflected from the steel strip and received by the antenna 44. The detector circuit 166 is responsive to the output signal from the separator circuit 100 to provide an output signal to the input circuit of a mixer circuit 103.

A source of modulation signals 116 has its output circuit connected to the input circuit of a signal source 118. The signal source 118 has a microwave signal generator circuit shown as a klystron circuit 120. The klystron circuit 120 provides a modulated 4output signal to a ferrite isolator circuit 122. The output circuit of the ferrite isolator circuit 122 is connected to the input circuit of a hybrid junction circuit 124. One output circuit of the hybrid junction circuit 124 is connected to an input circuit of the directional coupler 164, Thus, with this arrangement, a signal source 118 is provided which develops microwave energy which is applied to the input circuit of the directional coupler 104. This microwave energy is then transmitted to the antenna 44.

Similar to the antenna 44, the antenna 42 is coupled to a separator` circuit 110, having a slotted line or wave guide circuit and a directional coupler. The separator circuit 110 is also coupled to another output circuit of the hybrid junction 124 and the input circuit of a detector circuit 112, whose output circuit is coupled to another input circuit of the mixer circuit 108. Each of the output signals of the separator circuits 100 and 110 are proportional to the corresponding distances between the antennas 42 and 44 and the steel strip. This causes the output circuit of the detector circuits 106 and 112 to also provide output signals proportional thereto. A difference amplifier circuit 114 is connected to the output circuit of the mixer circuit 108 and the output circuit 47 of the desired thickness reference signal generator 48. The difference amplifier circuit 114 provides an output signal which is the. error signal to the amplifier circuit 50. The error signal is proportional to the difference between the output signal of the mixer circuit 108 and the output signal of the desired thickness reference signal generator 48. Further details of such a microwave thiclness detector are described in a copending application filed June 28, 1960, entitled Thickness Measuring Method and Apparatus, assigned to the same assignee as the present application, and bearing Serial No. 39,303 and now U.S. Patent 3,117,276.

It should be understood that the thickness detector unit 40 could also be a radiation gauge or a capacitive type of detector. In the capacitive type of detector the strip, whose thickness is to -be measured, is passed between two plates. Whenever material passes between the plates, the capacitance between them changes. This change in capacitance is detected and used to provide the error signal. An arrangement of this type is disclosed in the publication entitled Instruments and Control Systems for Iuly 1959, on pages 1038-1040.

Referring again to FIG. 1, the amplifier circuit 50 is connected to the output circuit of the microwave thickness detector unit 46. The amplifier circuit 50 provides a current output signal which varies above and below a current Io in accordance with the error signal applied to its input. The amplifier circuit 50 comprises conventional preamplifier circuits followed by a magnetic amplifier circuit for amplifying the error signal and for providing the above-mentioned current output signal. The output circuit of the amplifier circuit 50 is connected in parallel circuit relation to the coils in the magnetostrictive adjusters 24 and 39.

The mill screw-down control unit 38 has an adder and amplifier circuit 43. The adder and amplifier circuit 43 has one input circuit connected to an output circuit 49 of the desired thickness reference signal generator 48 and another input circuit is connected to the output circuit of the amplifier circuit 50. The adder and amplifier circuit 43 has a gain k1 which may be, but not necessarily, less than unity, and is operative to sum the input current from the desired thickness reference signal generator 48 with the input current from the amplifier circuit 50 and to provide positive and negative output currents directly proportional to the summation of these currents. The adder and amplifier circuit 43 has a very high input impedance so that only a negligible fraction, k2, of the output current of the amplifier circuit 5f) Hows into its input circuit. The output current from the output circuit 49 of the desired thickness reference signal generator 48 is a negative current signal with respect to the current out of the amplifier circuit 50. Thus, the output signal of the adder and amplifier circuit 43 is the difference between the magnitude of its two input current signals.

A sample signal unit 45 is also provided in the mill screw-down control unit 38 and has its input circuit connected to the output circuit of the adder and amplifier circuit 43. The output circuit of the sample signal unit 45 is connected to the input circuit of the direct-current compound motor unit 36.

The sample signal unit 45 is responsive to an input signal, with magnitude equal to or greater than Az'kl, to start developing a direct-current output signal of sufficient magnitude for energizing the armature circuit of the motor unit 36. Whenever the magnitude of an input current, of either polarity, to the sample signal unit 45 exceeds Az'kl, the sample signal unit 45 starts developing the directcurrent output signal and continues doing so until the input current drops to zero. When the input current drops -to zero, the direct-current output signal of the sample signal unit 45 drops to Zero.

A polarity responsive -control unit 33 is also arranged with a relay circuit (not shown) for reversing the connections of the field circuit of the motor unit 36 to reverse the direction of rotation of its output shaft.

Whenever the output current of the adder and amplifier circuit 43 has a positive output current whose magnitude is equal to or in excess of Az'kl, the polarity responsive control circuit 33 connects the field circuit so that the signal from the sample signal unit 45 energizes the motor unit 36 and causes it to decrease roll spacing. Whenever the output current of the adder and amplifier circuit 43 has a negative output current Whose magnitude is in excess of Akl, the polarity responsive control circuit 33 connects the field of the motor unit 36 so that current from the sample signal unit 45 energizes it and causes it to increase roll spacing. Whenever the polarity responsive control 33 switches the field of the motor unit 36, its operation should be essentially simultaneous with t-he start of the output current of the sample signal unit 45.

With the specific arrangement of FIGS, l1 and 2, `in rnind, a description of the `operation will be given with reference -to iFIG. 5. In the -following description the magnetostrictive adjuster 39 and the associated mill screw-down unit 41 are not specifically referred to, however, since they are -connected in parallel with the -magnetostrictive adjuster 24 and the mill screw-down unit 32, their operation is identical. FIG. 5 shows a graph of the displacement of the screw shaft 26 plotted against roll setting along the vertical coordinate and operating current in the coil 30 plotted along the horizontal coordinate. The roll setting along the vertical axis is without any deflection in the mill. Initially, the strip thickness h2 of the incremental :change in roll spacing is determined. The mill screw-down unit 32 and the signal at the output circuit 47 of the desired thickness reference signal 48 are adjusted such that an output current 2lo is developed by the amplifier circuit 50, when the thickness of the steel strip is at the desired strip thickness h2 (see FIG. l). Onehalf of the initial current 2Io ows in the coil of the magnetostrictive adjuster 24 and one-half of the current flows into the coil of the magnetostrictive adjuster 39. The initial value of current flowing into the coil 30, I0, is selected such that the screw shaft 26 is operated at about the center of the linear range of displacement. This corresponds to initial roll separation of ho. However, the spring constant of the mill and the forces created by the steel slab cause the rolls 12 and 14 to separate slightly rom this setting and the final thickness of the steel strip is h2 (see FIG. 1). The desired thickness reference signal generator 48 is also adjusted so that the output current is 2I0K2 or equal to the current fiowing into the input circuit of the adder and amplifier circuit 43. Thus, the output current of the adder and amplifier circuit 43 is initially zero. Thus, assuming the actual thickness of the steel strip is the desired thickness h2, the mill is now correctly adjusted and may -fbe set into operation.

After the mill operation has stabilized, assume that the thickness of the input steel slab increases or other conditions of the steel change causing increased pressure between the rolls 12 and 14, this causes an increase in the output thickness of the steel strip and an increase in 1z0 and h2. The output current of the thickness detector unit 40 will then increase by an amount directly proportional to the deviation in thickness of the steel strip from its preselected value. This causes an increase in the current in the magnetostrictive adjuster 24, causing the lower and 28 of the screw shaft 26 to elongate. When the length of the lower end 28 of the screw shaft 26 elongates, it exerts more pressure on the roll bearing 22 causing greater pressure on the steel slab and a reduction in the steel strip thickness. Conversely, a decrease in the output thickness of the steel strip from the preselected value will result in a decrease in the output current of the thickness detector unit 40. This causes a decrease of the current in the magnetostrictive adjuster 24 causing the lower end 28 of the screw shaft 26 to decrease in length and allow the roll spacing to increase.

Whenever the output current of the mill thickness detector unit 40 exceeds 2(10-j-Az`), or drops below the value 2Go-Ai), the mill screw-down control unit 38 develops a control signal causing the mill screw-down unit 32 to provide a coarse adjustment of the -roll spacing. Thus, it is seen that Whenever the output thickness of the strip decreases and the output current of the thickness detector unit 40 decreases, the initial decrease will be compensated for by the magnetostrictive adjuster 24. However, when the output current of the thickness detector unit 4t) drops below the predetermined value of 20o-Ai), the mill screw-down control unit starts to provide control signals to the motor unit 36 which causes it to rotate the screw shaft 26 and increase the roll spacing. The mill screw-down control unit 38 continues to provide the control signals to the motor 36 causing it to increase roll spacing until the output current of the thickness detector unit 40 is again at its initial value 21o. The output signal of the mill screw-down control unit 38 then stops, and stops the adjustment by the motor unit 36.

Similarly, whenever the thickness of the output steel strip increases, the output current of the thickness detector unit 40 increases until it exceeds the value 2(10-j-Az), where the mill screw-down control unit 38 starts to provide a control signal to the motor 36 which causes the screw shaft 26 to be adjusted so that the roll spacing decreases. The mill screw-down control unit 38 continues to energizes the motor 36 and decrease the roll spacing until the output current of the -thickness detector unit 40 again drops to 210.

It should be noted that the values of output current 2(1D-j-Az) and 2Go-Ai) were selected as the points where the mill screw-down control unit 3S starts energizing the motor circuit 36 and adjusting roll spacing. With reference to FIG. 5, it can be seen that the coarse adjustment by the mill screw-down circuit 32 will start being made before the lower end 28 of the screw shaft 26 is driven out of the linear range of magnetostriction. This is necessary since the coarse adjustment has a time delay and its operation must be started so that it will make the adjustments before the non-linear range of operation is reached.

It should be noted that the invention is not limited to a magnetostrictive adjuster which exerts its adjusting force on the top roll bearings, but the lower roll bearings could also be free to move in a vertical direction with the magnetostrictive adjuster arranged to exert pressure between the mill frame and the bottom surfaces of the lower roll bearings. Such an arrangement would allow the mill screw-down unit to make coarse adjustments on the upper roll bearings and the magnetostrictive adjuster would make roll adjustments on the lower roll bearings,

Another arrangement of importance within the scope of the present -invention is the use of two thickness detector units for detecting the thickness of the steel strip at both ends of the rolls and for individually adjusting spacing at both ends of the rolls.

Referring now to FIG. 2, magnetostrictive adjuster units 52 and 54 may be substituted for the magnetostrictive adjusters 24 and 39, for controlling roll spacing. The magnetostrictive adjuster 52 uses a portion of one side 56 of the mill frame as the adjusting element. A cell 57 is disposed about the side S6 of the mill frame l@ for providing a magnetic eldin the Iside 56. The magnetostrictive adjuster 54 is positioned on the other side 58 of the mill frame 10 with a coil 59. The mill frame 1) is made of material such as nickel or a ferrite which decreases in length when subjected to a magnetic iield. As current is increased in the coils 57 and 59, and the length of the sides of the mill frame 10 decrease, the roll spacing decreases. As current is decreased in the coils 57 and 59, there is an increase yin length of the sides of the mill frame 10 and an increase in roll spacing. Thus, it is seen that the coils 57 and 59 may be connected in parallel or in series to the output circuit of the thickness detector unit 40 and operate similar to the magnetostrictive adjusters 24 and 39.

lt should be understood that it is not necessary for the entire mill frame 1t) or even the sides S6 and 53 to be of a ferromagnetic material but only a portion of each side need be ferromagnetic to provide the desired positioning control.

FIG. 3 shows a mechanical amplifier arrangement using a magnetostrictive adjuster for controlling roll spacing. The mechanical amplifier comprises a stationary member 62 and a pivoted member 64. The stationary member 62 is an extension of the header of the mill frame 10 and has a shaft 66 for rotatably engaging one end of the pivoted member 64. The pivoted member 64 is a rectangular plate rotatably mounted on the shaft 66. The header of the mill frame also has a shoulder 68 extending out vertically. A magnetostrictive adjuster unit 70 is provided and comprises a magnetostrictive member 71 and a coil 75. The magnetostrictive member 71 is made of a positive magnetostrictive material and is positioned between the shoulder 68 and a point on the pivoted member 64 which is above the pivot point about the shaft 66. A screw shaft 72 has its lower end resting against the upper surface of the rolling bearing Z2 and extends up freely through a hole provided in the header of the mill frame 10. The upper end of the screw shaft 72 is threaded (not shown) for engaging with threads (not shown) in a sleeve 65. The hole in the header of the mill frame `10 for the screw shaft 72 has a sufficiently large opening along the length of the header that the pivoted member 64 and the screw shaft 72 rotate freely through the full lrange of `fine adjustment made by the magnetostrictive adjuster 70 without binding in the mill frame 10. The sleeve 65 is fitted inside a hole in the pivoted member 64 and fastened thereto by a pin 67. The upper end of the screw shaft 72 extends through the pivoted member 64 into a screw gear unit 74. The screw gear unit 74 is connected to an output shaft (not shown) of a motor unit 76. The screw gear unit '74 and the motor unit 76 are identical to the motor unit 36 and the screw gear unit 34 of FIG. 1.

The input circuit of the motor unit 76 may be connected to an output circuit of the mill screw-down control unit 38. The c-oil is connected to an output circuit of the amplifier circuit 50. The other side of the mill frame 10 has a similar mechanical amplifier ar-rangement (not shown) for applying adjustments to the bearing 20. The motor unit 76 -is responsive to input signals from the mill screw-down control unit 38 to rotate the screw shaft 72 and thereby provide a coarse adjustment in the roll spacing. The magnetostrictive adjuster 70 is responsive to changes in the cur-rent signals in the coil to cause the ferromagnetic member 71 to elongate and decrease in length and thereby cause the pivotedmember 64 to pivot about the shaft 66 and increase and decrease roll pressure.

An alternate mechanical amplier arrangement is shown in FIG. 4. The structural arrangement of FIG. 4 is similar to that shown in FG. l, however, the magnetostrictive adjuster 24 is replaced by the magnetostrictive adjuster 8i) which provides mechanical amplification. The magnetostrictive adjuster 80 comprises members 82, 84, 86, and 8S. The members are connected together by pivoted joints and another member 89 is connected between the pivoted junctions formed by the junction of the members 9 82 and 86, and the members 84 and 88 so that the resultant structure is a rigid parallelogram. The junction of the members 82 and 84, and the members 86 and S8 are positioned at a lower end ofthe screw shaft 26 and the roll bearing 22.

The members S2, S4, 86, and 88 are all made of a positive ferromagnetic material which expands when subjected to a magnetic field, whereas the member 89 is made of a negative ferromagnetic material which decreases in length when subjected to a magnetic field. Coils 92, 94, 96, 98, and 99 are disposed about the members 82, 84, S6, 88, and 89, respectively. All of the coils may be connected in parallel to the output circuit of the amplifier circuit Sil.

When current is passed through the coils of the magnetostrictive adjuster 80, it causes each of the postive magnetostrictive members to simultaneously increase in length. An increase in current in the coil 99 causes the negative magnetostrictive member S9 to decrease in length. As a result, there is a decrease in roll spacing. Similarly, a decrease in current in the coils 92, 94, `96 and 98 cause an increase in roll spacing. This will then be seen to provide a mechanical amplification of the roll displacement relative to the displacement provided by a single magnetostrictive unit as shown in FIGURE l.

AAlthough the magnetostrictive adjusters described in FIGS. l, 3 and 4 have been shown with only one ferromagnetic member, magnetostrictive adjusters may be provided with an even number of ferromagnetic members in parallel to insure a return flux path through a magnetostrictively active material. When, for example, only one ferromagnetic member is used, the return iiux path must either be through the surrounding air or through the cast iron or steel mill frame 10 which would cause a deteriorating effect on the linearity and hysteresis of the magnetostrictive characteristics of the members. Thus, it should be understood that each of the ferromagnetic members described above may have two ferromagnetic members arranged in parallel relationship, such as that shown in FIG. 7.

With the description of operation of FIG. l in mind, it should now be evident that sudden small Changes of strip thickness may also be indicated by a pressure sensitive device based on the magnetostrictive principle. The signal from this device may Iact to trigger a certain preselected correction by the magnetostrictive adjusted. A specific application of this may be to compensate for inhomogeneities of welds of two steel strips in a continuous operation of strip rolling.

It should `be noted that it is important from a strength standpoint to maintain a low length-to-width ratio for each ferromagnetic member, whereas from a power consumption standpoint t'ne overall volume of material should be kept to a minimum. This means that if the -per unit magnetostrictive is increased to `a maximum, thereby allowing the length of the ferromagnetic members to be kept to a minimum, the Volume of the material may be minimized. As a result, materials and treatments of materials considered in selecting material for the ferromagnetic member to provide maximum magnetostrictive action per unit length are: alloys of non-ferrous elements and ferrous elements, amounts of impurities, work hardening, annealing and magnetic annealing. Another important consideration is loading of the ferromagnetic member. -A member made from a positive ferromagnetic material should be magnetostrictively operated under compression, whereas a negative magnetostrictive material should be operated in a state of tension, as opposed to the opposite loading. These factors should be used to best advantage in order to optimize the magnetostrictive action of the ferromagnetic members. As an example, an alloy of 70% cobalt and 30% iron rolled in the direction of applied magnetic field has been found to exhibit about 130+ 10-6 inches elongation per inch for -a field of 130() oersteds.

From the above discussion it should be evident that the shape of each ferromagnetic member is important and, -as a result, the members may be constructed in a variety of preferred shapes. Thus, the ferromagnetic members may be a solid cylindrical member such as that in FIG. 8, or a tubular member such as that shown in FIG. 9, or scroll type of members such as that shown in FIG. 10. In the scroll type of members arrangement shown in FIG. l0, the scroll 'of ferromagnetic material must be bonded together rigidly so as to avoid mechanical creeping or motion between the laminations.

It should be evident from the above detailed description of this invention that there are a number of other important applications of the present invention than a steel rolling mill. For example, other objects or profiles may be rolled in a rolling mill than steel slabs. Also, horizontal `or other angular adjustments may be made as well as vertical adjustments without departing from the present invention. Another example would be the use of magnetostrictive adjusters for the control of the movement of plates in a printing press and, more particularly, in a multi-color printing system. In such a printing system a light could be aranged to fiash and indicate a finishedprinting operation. A fast responding photocell circuit could then be used to monitor the registration of the finished printing. The output signal of the photocell could then be used to energize control circuitry which in turn would provide the necessary current in the magnetostrictive adjuster to control the pressure on the plates.

What is claimed is:

1. A rolling mill for rolling material into profiles, comprising lat least two rolls arranged for exerting forces and controlling the thickness of a material passed therebetween, at least one of said rolls being movable in response to the material passing between said two rolls, and a magnetostrictive adjusting unit mounted with said movable roll for opposing the motion thereof, and means for detecting the thickness of said material as it emerges form said rolls and for providing an electrical signal to the magnetostrictive adjusting unit indicative of the desired thickness of the material, said magnetostrictive adjusting unit being responsive to the electrical signal and positioned so as to effect incremental changes in the roll spacing.

`2. A rolling mill for rolling slabs of material into strips of uniform thickness comprising: a stantionary member; at least one roll for applying pressure to a slab of material passed between said roll and said member for compressing said material to a desired thickness; a mill frame for supporting said member and for guiding said roll; -at least one pair of magnetostrictive adjusting units mechanically connected at opposite ends of said roll for providing tine adjustments in the pressure applied and thereby spacing between said roll and said member in response to applied electrical signals; and means for detecting the reduced thickness of the slab of material emerging from between said roll and said member and for providing `a corresponding electrical signal to said magnetostrictive units.

3. A rolling mill as defined in claim 2, including bearings for rotatably mounting said at least one roll in said mill frame, said magnetostrictive adjusting units each comprising a ferromagnetic member, having magnetostrictive properties, mechanically coupled between said mill frame and said bearings and at least one winding for passing a magnetic field through said ferromagnetic member in response to said electrical signal for controlling reduced thickness of said material.

4. A rolling mill as defined in claim 2 wherein said magnetostrictive adjusting units each include a mechanica-l amplifier for amplifying the changes in roll pressure.

5. A rolling mill as defined in claim 4 wherein said mechanical amplifier comprises four ferromagnetic members hinged together at their ends so as t-o form a parallelogram and at least one cross member for connecting between hinged ends of said parallelogram structure so as to form a rigid structure.

6. A roll control unit for compensating for the fine incremental changes of the spacing of rolls, a mill frame of a rolling mill comprising: a screw shaft for exerting pressure between the bearing of a roll and the mill frame, said screw shaft including a portion having magnetostrictive characteristics; and at least one electrical winding disposed about said screw shaft portion for inducing a magnetic field therein for controlling the length `of said kscrew shaft.

7. A roll control unit as defined in claim 6 wherein said screw shaft portion includes an even number of members having magnetostrictive characteristics, connected together at the ends to form a closed magnetic loop through said members, and at least one winding disposed about each of said members.

8. A roll control unit as defined in claim 6 wherein said screw shaft portion includes at least one cylindrical member.

9. A roll control unit as defined in claim 6 wherein said screw shaft portion includes at least on-e sheet of material, having magnetostrictive characteristics, rolled in a scroll and bonded together to form a rigid member.

10. A roll control unit as defined in claim 6 wherein said screw shaft portion includes at least one tubular member exhibiting magnetostrictive characteristics.

11. In a control system including a pair of elements arranged for forming, shaping, or profiling the physical dimensions of a material passed therethrough, at least one of said elements being movable with respect to the other, said movable element including a portion exhibiting magnetostrictive properties and having an electrical winding coupled to said portion, means for measuring the c-ontrolled dimension of the material as it emerges from the elements, a source of reference signals proportioned to have a value proportional to the desired dimension for the material, means for comparing the measured dimension with the desired dimension and providing an -output difference signal corresponding thereto, and means for controlling the position of said movable element including circuit means connected to said comparing means having an electrical connection to said electrical Winding and responsive to the difference signal.

12. A ro-lling mill including a pair of rolls arranged for shaping material passed therebetween into a strip of material having a certain desired thickness, means for measuring the actual thickness 1of the material emerging from said rolls and for providing an indication of the actual thickness thereof, means for providing an indication of the certain desired thickness `of the material, means adapted for comparing the actual thickness indication and the certain desired thickness indication and for providing an error signal indicative of the difference therebetween, means connected for controlling the spacing of the rolls and thereby control the thickness of the materia-l emerging therefrom including motor means adapted to be responsive to values of said error signal indicative -of deviations -of the actual material thickness from the desired material thickness in excess of a predetermined large deviation for providing a coarse corrective adjustment in the spacing of the rolls, and including a separate electro-mechanical roll position adjusting means adapted to be responsive to said error signal for continuously affecting a fine corrective adjustment in spacing to the rolls corresponding to said error signal.

13. In a control system including a pair of elements arranged for forming, shaping, or profiling material passed therebetween, at least one of said elements being movable with respect to the other, said movable element including a portion exhibiting magnetostrictive properties which is positioned for exerting a control force ion said movable element and thereby exert a force on the material passing between said elements for controlling a desired physical dimensionl of the material emerging from said elements,

means positioned for measuring the controlled dimension of the material emerging from said elements and for providing an output signal indicative `of a deviation -of the controlled dimension of the material from a desired dimension, and electrical winding means coupled to be responsive to said output signal for inducing a magnetic field in said magnetostrictive portion for controlling the force exerted by the elements on the material passing therebetween and for determining the controlled dimension of the emerging material.

14. In a control system as defined in claim 13 wherein said magnetostrictive portion lof the movable element includes an even number of members connected to form at least one closed low reluctance magnetic fiux path between the Iends of the members, each of the members exhibiting magnetostrictive properties and being arranged for individually exerting a force on said movable element, said electrical winding means including an electrical winding for each of said members.

15. A rolling mill including a pair of rolls for rolling material passed therebetween into a strip of uniform thickness, at least one of said rolls being movable with respect to the other, electro-mechanical means for exerting a control force on said movable roll and thereby exert a force on the material passing between said rolls for controlling the final thickness thereof, and means for measuring the thickness of the emerging material and for providing a control signal indicative thereof, said electromechanical means comprising at least one member exhibiting magnetostrictive Properties and electrical winding means coupled to be responsive to said control signal for inducing a magnetic field in said at least one member, said at least one member being positioned for exerting a control force on said movable roll in response to the :magnetic field induced therein `for control-ling the thickness of the emerging material.

16. A rolling mill as defined in claim 15 wherein said at least one member includes a mechanical amplifier comprising at least four members connected together end to end to form a closed loop, and at least one cross connecting member connected between the members in the loop to form a rigid structure, each of said at least four members exhibiting magnetostrictive characteristics, and winding means coupled for inducing a magnetic field in each of said at least four members in response to said control signal.

17. A rolling mill as defined in claim 15 including a mechanical amplifier comprising a pivoted member having an extending member for engaging said movable roll, said at least one member being positioned for exerting a force on said pivoted member tending to rotate same and thereby control the thickness of the emerging material in response to said control signal.

1S. In a rolling mill for rolling material into strips of uniform thickness including: a pair of rolls positioned for exerting a force on material passed therebetween, at least one of said rolls being movable away from the other of said rolls in response to the pressure of material passing therebetween; a source of reference signals having a value corresponding to the desired thickness of the material emerging from the rolls; means for detecting the thickness of the material emerging from the rolls and for providing an electrical indication thereof; an electrical circuit connected for comparing the reference signal and the electrical indication and for generating an electrical signal indicative of the difference between the desired thickness and the actual thickness of the emerging material; at least one screw down unit including a screw shaft positioned for exerting a force on said movable roll opposing the movement thereof caused by the material passing between the rolls; and at least one control unit connected to be responsive to a value of said electrical signal indicative of a larger deviation of the thickness of the emerging material from the desired thickness for applying a corresponding control signal to said screw down unit, said screw down unit being responsive to the applied signal of said control unit for providing a coarse adjustment in the pressure of said screw shaft on said movable roll and thereby provide a coarse corrective adjustment in the thickness of the emerging material, said screw shaft including a portion exhibiting magnetostrictive properties and an electrical winding, said electrical winding being coupled to be responsive to values of said electrical signal indicative of a small deviation of the emerging material thickness from the desired material thickness, which is less than the large deviation for inducing a magnetic iield in said magnetostrictive portion of the screw shaft, causing the magnetostrictive portion of the screw shaft to provide a fine mechanical adjustment in the pressure on the movable roll for providing a corrective adjustment in the thickness of the emerging material.

19. A rolling mill including a pair of rolls arranged for shaping material passed therebetween into a strip of material having a desired thickness, means for measuring the actual thickness of the material emerging from said rolls and for providing an indication of the actual thickness thereof, means for providing an indication of the certain desired thickness of the material, means connected to be responsive to the actual thickness indication and the certain desired thickness indication for comparing same and for providing an error signal indicative of the difference therebetween, and means connected for forcing the rolls together thereby opposing the force on the rolls due to the material passed therebetween for controlling the thickness of the emerging material comprising rst electro-mechanical roll positioning means adapted to be responsive to values of said error signal above a preselected amount for affecting a rst corrective adjustment in roll spacing, and second electro-mechanical roll positioning means adapted to be responsive to values of said error signal below the preselected amount for affecting smalled corrective adjustments in roll spacing.

20. A rolling mill including a pair of rolls arranged for shaping material passed therebetween into a strip of material having a desired thickness, means for measuring the thickness of the material emerging from -said rolls and including circuit means for forming a first signal indicative of a iirst large deviation of the emerging material from the desired thickness and for forming a second signal indicative of a second smaller deviation therefrom, means connected for forcing the rolls together thereby opposing the force on the rolls due to the material passed therebetween and for controlling the thickness of the emerging material comprising iirst electro-mechanical roll positioning means adapted to be responsive to said first signal for providing a corresponding large corrective adjustment in roll spacing, and second electro-mechanical roll positioning means adapted to be responsive to said second signal for applying a corresponding finer corrective adjustment in roll spacing and thereby compensate for deviations of the emerging material from said large correction.

21. A method for rolling material to a predetermined thickness including the steps of rolling the material between a pair of rolls, forcing the rolls together to cause pressure between the rolls on the material such that the material emerging from the rolls is rolled to a predetermined reference thickness, continuously measuring the thickness of the material as it emerges from the rolls, continuously forming a first electrical signal indicative of the deviation of the emerging material from the reference thickness and forming a second electrical signal indicative of a preselected large deviation of the emerging material from the desired thickness, the step of forcing the rolls together including the steps of applying a first large corrective change in the roll spacing to correct the thickness of the emerging material in response to said second signal, and continuously applying a separate, ner corrective change in the roll spacing to correct for smaller deviations in thickness of the emerging material in accordance with the deviation indicated by said first signal.

22. A method for controlling the thickness of a material by controlling the spacing of rolls, including the steps of passing a material between a pair of rolls arranged to control the thickness of the material to a predetermined reference thickness, continuously measuring the thickness of the material as it emerges from the rolls and continuously forming an electrical error signal indicative of any difference in thickness from the reference thickness, applying a first large corrective adjustment to the rolls to correct the spacing thereof when the error signal exceeds a preselected amount, and continously applying a finer corrective adjustment to the rolls to correct for 4the spacing of the rolls corresponding to said error signal.

23. A method for controlling the thickness of a material passing through the rolls of a rolling mill having a mill screw-down unit including the steps of electrically controlling the mill screw-down unit to cause the rolls to have a predetermined separation as material is passed therethrough to thereby cause the material passed to assume a preselected thickness, continuously passing a material to be controlled in thickness through the rolls, continuously measuring the thickness of the material as it emerges from the rolls, comparing the measured thickness of the material with a preselected thickness and providing a signal indicative of the diierence between the preselected thickness and the measured thickness, controlling the mill screw-down unit to cause a iirst change in the position of the rolls when the difference signal exceeds a predetermined amount, continuously applying a ner corrective adjustment to the rolls to cause a tine corrective change in the material thickness in accordance with said dierence signal.

References Cited bythe Examiner UNITED STATES PATENTS 2,264,095 11/41 Mohler 80-32.1 2,564,284 8/51 Schurr 80-56 2,640,190 5/53 Rmes 324-61 2,788,457 4/57 Griest 73-67 2,978,648 4/61 Harris 330-60 3,062,078 11/62 Hulls 80-56.2 3,081,654 3/63 Wallace 80-56.2

FOREIGN PATENTS 571,793 3/59 Canada.

WILLIAM I. STEPHENSON, Primary Examiner.

THOMAS E. BEALL, LEON PEAR, Examiners.

UNITED STATES PATENT oFEICE CERTIFICATE OF CORRECTION Patent No. 3,216,231 November 9, 1965 Bertil S M. Granborg l It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 73, for "cell 57" read Coil 57 column 9, line 45, for "adjusted" read adjuster line 54, for "magnetostrictve" read magnetostrction column 10, line 23, for "fnishedJ' read fnshline 38, for form" read from line 16, for "stantonary" read Stationary line 53, strike out app1ied"; column 13, line 37, for "smalled" read smaller Signed and sealed this 27th day of September 1966.

CSEAL) ttest:

ERNEST W. SW'IDER EDWARD I. BRENNER Attesting Officer Commissioner of Patents 

1. A ROLLING MILL FOR ROLLING MATERIAL INTO PROFILES, COMPRISING AT LEAST TWO ROLLS ARRANGED FOR EXERTING FORCES AND CONTROLLING THE THICKNESS OF A MATERIAL PASSED THEREBETWEEN, AT LEAST ONE OF SAID ROLLS BEING MOVABLE IN RESPONSE TO THE MATERIAL PASSING BETWEEN SAID TWO ROLLS, AND A MAGNETOSTRICTIVE ADJUSTING UNIT MOUNTED WITH SAID MOVABLE ROLL FOR OPPOSING THE MOTION THEREOF, AND MEANS FOR DETECTING THE THICKNESS OF SAID MATERIAL AS IT EMERGES FORM SAID ROLLS AND FOR PROVIDING AN ELECTRICAL SIGNAL TO THE MAGNETOSTRICTIVE ADJUSTING UNIT INDICATIVE OF THE DESIRED THICKNESS OF THE MATERIAL, SAID MAGNETOSTRICTIVE ADJUSTING UNIT BEING RESPONSIVE TO THE ELECTRICAL SIGNAL AND POSITIONED SO AS TO EFFECT INCREMENTAL CHANGES IN THE ROLL SPACING. 